1. Field of the Invention
The present invention relates to an improvement in the system for detecting the slipping of railway vehicles.
2. Description of the Prior Art
A railway vehicle has a plurality of wheels driven by motors, i.e., driving wheels, and it is common practice to control each motor to attain the same current value. When a driving wheel slips, the current of the motor driving that driving wheel is reduced. If this situation is left as it is, the control system works in such a manner as to increase the current of the motor, resulting in an aggravated slipping.
In a conventional control system, the reduction of the motor current is detected and if the degree of reduction exceeds a predetermined value, the slipping of the driving wheel driven by that particular motor is detected. The general current command is then reduced to attain "readhesion", i.e., renewed frictional engagement between the rail and wheel.
In this conventional system for detecting the degree of reduction of the motor current, the current is monitored for each motor and therefore the system is both bulky and uneconomical. It is also impossible for this system to detect a slipping with high accuracy taking into consideration the difference in diameter among the driving wheels, the difference in characteristics among the motors and the difference in slip detection level with speed.